The wireless communication technology has undergone development phases from analog communication to digital communication, from single carrier (Single carrier) communication to multi-carrier (Multi-carrier) communication, from single-mode (Single-Mode) communication to multi-mode (Multi-Mode) communication. At present, a multi-frequency band (Multi-Frequency Band) communication technology becomes a next hot topic that manufacturers of communications devices and research institutes focus on.
The frequency band refers to spectrum resources distributed in certain bandwidth, and the multi-frequency band refers to a combination of two or more frequency bands separated by a certain distance at a spectrum. For example, in a UMTS (Universal Mobile Telecommunications System, universal mobile telecommunications system), a frequency band Band 1 has a downlink of 2110 MHz to 2170 MHz and an uplink of 1920 MHz to 1980 MHz. In the TD-SCDMA (Time Division-Synchronous Code Division Multiple Access, time division-synchronous code division multiple access), a frequency band A is 1880 MHz to 1900 MHz, and a frequency band B is 2010 MHz to 2025 MHz. The multi-frequency band may be a combination of frequency bands for different standards, for example, frequency bands for the UMTS and the LTE (Long Term Evolution, long term evolution); and may also be a combination of different frequency bands for the same standard, for example, the frequency band A and the frequency band B in the TD-SCDMA.
A multi-frequency band telecommunications system is also referred to as a multi-standard telecommunications system. In the multi-frequency band telecommunications system, a transceiver (Transceiver) may receive and send radio frequency signals on multiple frequency bands at the same time. A key apparatus in the multi-frequency band telecommunications system is a multi-frequency band transceiver. At present, an applied solution of the multi-frequency band transceiver is referred to as a multi-density transceiver. The multi-density transceiver directly uses multiple sets of discrete components to constitute multiple radio frequency channels to process different frequency band signals, or uses a highly integrated semiconductor process to integrate multiple radio frequency transceiver channels inside one same system in a package (System in a package, SIP) or an IC (Integrated circuit, integrated circuit). A set of signal processing channels usually includes a downlink channel, an uplink channel and a feedback channel. The downlink channel usually includes modules such as a digital part, a digital analog converter, a modulator or a mixer, an amplifier, a power amplifier, and a frequency band filter, and the uplink channel usually includes modules such as a frequency band filter, an LNA (Low Noise Amplifier, low noise amplifier), an amplifier, a mixer or a demodulator, an analog digital converter, and a digital part.
However, for the practice that multiple radio frequency transceiver channels are integrated in one same system in a package or an IC by using the highly integrated semiconductor process, there is a problem whether an isolation degree and performance of the radio frequency signal of different frequency bands can satisfy protocol requirements. When multiple sets of discrete components directly constitute multiple radio frequency channels to process different frequency band signals, the problem of the isolation degrees and the performance of different frequency bands may be solved, but the problems that the apparatus has a huge volume, high power consumption, and a high cost occur. Similarly, the multi-frequency band signal brings about higher requirements for the bandwidth supported by the feedback channel, and the problem same as that in the multi-radio frequency transceiver channel also exists in the multi-channel solution of the feedback channel.